This project will address the need for real-time, continuous measurement of radiation dose in vivo. Under Phase I, the feasibility of developing a microelectronic fabrication process for simultaneous manufacture of radiation sensing field effect transistors (RADFETs) and ordinary transistor devices on a single silicon substrate was successfully demonstrated. Smart radiation sensors and miniature probes with linear arrays of sensors will be designed and manufactured under Phase II. Microelectronic circuits for detection, signal processing. A/D conversion, and computer interfacing will be designed, manufactured, and evaluated. Software for probe control, data acquisition, and real-time data display will be developed. These component systems will be assembled into a multisite, digital output radiation dosimetry probe that will be evaluated in phantoms emulating in vivo measurements in advance of Phase III studies in the clinic. Two-dimensional arrangements of the miniature sensors will permit dose imaging. Each year approximately 1 million new cases of cancer are reported in the US alone; nearly 600.000 of those cases are treated with radiation. Radioimmunoassay therapy (RIT) is currently under investigation and in clinical trials as a novel technique of targeting tumors. Stereotactic radiotherapy with attendant large dose gradients is growing. The instrument will allow real time dose rate and total accumulated dose measurements during RIT and stereotactic radiotherapy treatment. This information, unobtainable by current techniques, will result in better pre-treatment planning and post-treatment evaluation as well as potential optimization of radiation exposure during radioimmunotherapy. PROPOSED COMMERCIAL APPLICATION: This development will lead to the first array of radiation sensors which provide both real-time dose rate and total dose for in vivo applications. While initially motivated by strong interest in quantifying the potential or radioimmunotherapy, the sensors should also find wide application in brachytherapy, stereotactic radiotherapy. in investigational settings and use as an on-patient monitor. Dose images derived from 2-D arrays of sensors placed on the patient has significant potential.